<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        .content { 
            width: 400px; 
            height: 400px; 
            box-sizing: border-box; 
            padding: 5px; 
            border-radius: 50%; 
            background-image: -webkit-linear-gradient(top, red 0%, blue 30%, yellow 60%, green 90%); 
            background-image: -moz-linear-gradient(top, red 0%, blue 30%, yellow 60%, green 90%); 
            background-image: linear-gradient(top, red 0%, blue 30%, yellow 60%, green 90%); 
        } 
        .box { 
            width:100%; 
            height:100%; 
            border-radius:50%; 
            background:#fff; 
        }
    </style>
</head>
<body>
        <div class="content">
            <div class="box"></div>
        </div>
</body>
</html>